with Coach Dandelion Dilluvio-Scott

In the spring of 2022, I was preparing to move from the Puget Sound Region of Washington State to the  foothills of the Wind River Range in Wyoming in early fall. I was, of course, caught up in important moving preparation activities like panicking that all our stuff wouldn’t fit into the truck. In between trips to the dump in an effort to purge and ensure everything would indeed fit in the truck, I found myself pondering how my body would react to the long-term change in altitude. As a mountain athlete living in Washington, I spent a respectable amount of time at elevations between 6,000-14,000 feet. Despite this regular exposure I was never truly acclimated to high elevation. In Jason Koop’s book Training Essentials  for Ultrarunning- Second Edition he notes that true adaptation takes 2-4 weeks of continuous exposure to achieve. Being that my time in the high mountains leading up to the move would be limited mostly to  weekend adventure runs and mountaineering excursions I was certainly not going to meet the dosage requirement. This posed a problem for two reasons. One, feeling sluggish for up to a month upon arriving in the Wind River Range seemed like the opposite of delightful. Two, I wanted to race the Run the Red Desert 100k a week after my arrival to Wyoming. After contemplation and research, I decided that the best option to solve this conundrum was to deploy the use of an Altitude Tent. 

Acclimating with at Altitude Tent: A Brief Review of the Science 

An altitude tent allows an athlete to acclimate through normobaric hypoxia exposure. More simply, this means replicated altitude. When you are standing on top of a summit like Grand Teton, there is a lack of oxygen density. Therefore, oxygen availability to the body is limited as a result of low air pressure. To  imitate this environment an altitude tent lowers the concentration of oxygen using a generator/pump  device that removes some oxygen from inside the tent chamber and replaces it with nitrogen while the air pressure remains unchanged. 

In the end, normobaric hypoxia exposure will elicit the same body response and adaptations as  hypobaric hypoxia exposure (ie: standing on the summit of Grand Teton). In either scenario, long term  exposure to either real or “fake” altitude will cause the body to go through a series of changes in  response to the decreased oxygen availability. In the short term, ventilation or breathing will increase  and a person may experience increased fluid loss leading to dehydration. As time goes on the body will begin to acclimate and increase the production of red blood cells and capillaries. Ultimately this allows  the body to transport more oxygen and, therefore, somewhat counterbalance the lack of available  oxygen at altitude.  

Is an Altitude Tent Right for you? 

A quick review of the section above might lead you to believe that an altitude tent is an ideal  contraption. It sounds like the perfect solution for an athlete preparing for a high elevation race without  the luxury of arriving at the destination with enough time to acclimate via hypobaric hypoxia exposure. 

However, one should proceed with caution when choosing to utilize an altitude tent as part of race  preparation. Altitude tents are not without flaws and, sometimes, these imperfections can offset any  benefit they might otherwise introduce to your training regimen. Take these items into consideration before you click the “place order” button:  

Considerations: 

1. It Ain’t Cheap: Altitude tent setups can cost upwards of $2,000. It is not a small gadget that you  buy on a whim. This is an investment! Therefore, be sure to do your homework both by reading  further in this article and doing some additional research. Many altitude tent companies offer  tent rentals and some even have a rent-to-buy option. I highly recommend taking the rental  route if available so you can test the product and find out if it will fit in your training and lifestyle  needs.  
2. Higher is not Better: Some companies sell a diverse selection of generators with different max  altitude levels. For running purposes, a system that can reach 10,000ft will suffice. Sleeping in an  environment above this level will not harm you, but there is no added benefit as described in Jason Koop’s book Training Essentials for Ultrarunning- Second Edition. 
3. Humidity and Heat: You are effectively sleeping in a (mostly) plastic bubble with very little  ventilation. Sooner or later the confines of the tent will begin to feel like a steam sauna complete  with humidity. Of course, with humidity comes condensation. In a dry climate condensation will  simply come in the form of minor dampness on the inner tent walls. However, in a high humidity  atmosphere the condensation can accumulate to the point where you get rained on every time you roll over in your sleep and happen to touch the tent walls! To combat these unpleasantries you may need to invest in a mattress cooling system on top of the already pricy altitude tent in order to get a good night’s rest and properly recover. 
4. The Ruckus: There are two noise making mechanisms associated with a tent setup: The pump and the generator. The generator’s motor emits a somewhat loud humming sound throughout the night. To some this is white noise and not an issue. Others will find the constant drone irritating making it impossible to fall asleep. The pump action of the mechanism can cause  further disturbance. A tube runs from the generator into the tent to regulate the oxygen. With each pump there is a puff of air that makes a sound akin to a St. Bernard breathing very heavily in your ear. Again, this is a non-issue for some and a huge concern for others.  
5. Time & Daily Elevation: You’ll recall from the first paragraph that it takes 2-4 weeks for an athlete to acclimate while living at high elevation 24/7. The altitude tent will only be used during sleep which amounts to 7-10 hours per night for most folks. Once you leave the tent any adaptation gains are compromised. Jason Koop notes in his book, Training Essentials for Ultrarunning- Second Edition, that there is no official protocol for how many nights one needs to use an altitude tent to achieve full acclimation. Furthermore, no one fully understands how the daytime elevation of the athlete affects the speed of acclimazation or the tent’s effectiveness overall for that matter. For example, a person living at 500ft will likely respond differently sleeping in an altitude tent than a person spending their daytime hours at 6,000ft. Therefore, any regimen you set will mostly be trial and error and not based wholly on science.  
6. Your Partner: If you sleep with a partner their sleep patterns and tendencies will need to be taken into account in addition to your own. Perhaps you’re unbothered by noises, but the sound of the pump will keep your partner up all night glaring at you in disdain. Or, more simply, maybe your partner doesn’t like the idea of sleeping in the confines of a tent regardless. In short, talk to your partner before committing to a tent! 

My Experience with An Altitude Tent  

Circling back to spring 2022… I considered each available brand when I made the decision to use an  altitude to prepare for both training regularly at high elevations and Run the Red Desert 100k.  Ultimately, I settled on renting (and later purchasing) the MountainAir Complete System Automatically  Controlled Altitude Tent. This particular model provided mitigation measures to soften (not eliminate)  the inherent issues of altitude tents. My detailed review of the tent can be found here.  

It’s not recommended that you immediately set the tent to 10,000ft on your first night. It is best to  slowly “climb” the mountain. I set the tent to 5,000ft to start with the plan of increasing the vert by  500ft every night until reaching 10,000ft. This ascent rate was a bit too hasty and sleep quality was inhibited so I dialed it back and added 500ft every 3-4 nights.

For about two weeks I noticed myself breathing rapidly while in the tent and I could absolutely tell when I zipped the door shut that the concentration of oxygen differed from that just beyond the confines of the tent chamber. I did not notice any difference in my sleep patterns or recovery. Meanwhile my husband was unable to sleep well in the tent regardless of the elevation setting and began spending the night on the couch while I continued my acclimation process in the tent. I’m lucky he was so patient while I experimented with the tent and we have since worked out a schedule with tent use frequency so we don’t need to sleep separately every night! It took about 4 weeks of using the tent on weeknights for my breathing to even out and to not notice a  difference in the air within the interior versus exterior of the tent.

As there is no protocol for altitude tent dosage, I simply planned on using the tent nearly every night whenI wasn’t sleeping at natural elevation in the mountains. I followed this strategy diligently right up until the 90+ degree days of summer arrived. At this temperature the air conditioner, a fan inside the tent and our newly acquired mattress cooling system combined couldn’t bring the climate inside the tent to equilibrium. On those nights I’d wake up covered in sweat and hastily unzip the tent doors as condensation fell from the ceiling creating a not a no so pleasant midnight drizzle. I learned after a few nights of this fiasco that when the external temperature verged on sweltering it was best to just sleep with the tent doors open and the generator silent. By this time, I’d spent nearly 3.5 months sleeping in the tent with little interruption. I theorized that my body was acclimated well enough that taking a few days off here and there would not cause a significant decline in adaptation so long as I slept in it 2-3 nights a week and spent weekends at naturally high elevations. 

In August,  I decided to attempt an adventure run up and down Mount Rainier in a day. I had summited the 14,411ft glaciated volcano traditional style several times prior to this excursion. During those previous ascents I experienced some version of sluggishness and/or nausea on the upper reaches of the climb  and wondered if and how sleeping in the altitude tent would affect my performance  on this car-to-car adventure. The verdict? I set PR after PR on this ascent of Rainier. Part of this was attributed to increased overall fitness since my last ascent and completing the climb using lite/and fast methods (trail runners and vests instead of mountaineering boots and 60lb packs for example). However, even though I definitely felt the altitude as I ascended, my pace did not turn into a sluggish trudge nor did I feel any hint of nausea. Instead, my steps merely slowed a bit as I continued upward at a steady pace to the summit. I have no way to measure what percent of the performance increase was accredited to the use of a tent. However, I believe it did play a factor.  

A month later I found myself at 7,440ft at the start line of Run the Red Desert 100k. It had been about 12 days since I last slept in the altitude tent as it was still packed in a box and that box was likely  somewhere at the very bottom of the giant pile of boxes in our living room. However, I’d spent the last week living at 5,500ft and training on trails at 7,500-8,000ft. When I stepped off the start line at Run the Red Desert 100k I felt normal. The altitude was a none-issue for me during the race and, in fact, it was my best race performance to date. Again, I do not know what percentage of my performance was  fitness-based v. acclimation-based. I can say that I chatted with several racers from lower elevations  who were very fit, but struggling with the altitude on various levels. In my opinion, using the altitude  tent in conjunction with training at altitudes above 6,000ft at least once a week in the months leading  up to Run the Red Desert 100k played a role in enhancing my performance.  

The experience and conclusion I described above is just that: my experience and my conclusion. It is not a scientific study using proper procedures, a large sample of athletes or control groups. You may have a completely different experience using the altitude tent. However, I hope that my story provides insight to athletes considering the use of this piece of specialized equipment as part of their race preparation. As for me, I continue to use the tent as part of my training and will remain doing so as long as it doesn’t impact my sleep quality and recovery. Happy acclimating!

Dandelion Dilluvio-Scott is a coach with Team RunRun. To learn more about her or to work with her, check out her coach profile.